Despite significant advances in the treatment of patients harboring GBM, there have been modest increases in overall survivals, on the order of 1 month for every decade of research. While the EORTC-NCIC trial by Hegi et al (13) implicated the status of MGMT promoter methylation as a biomarker of GBM patient response to Temozolomide (TMZ), all GBM patients continue to be treated with TMZ, regardless of their MGMT status (13). The lack of enthusiasm to systematically use MGMT promoter methylation to guide treatment is due to: 1) lack of other therapeutic options; 2) 50% of patients with methylated MGMT promoter (a good prognostic factor) do not survive 2 years; and, 3) 15% of patients with unmethylated MGMT promoter (bad prognosis) survived 2 years. Moreover, MGMT methylation status is associated with improved outcome both in the TMZ-based chemoradiation and radiation-only arms. All of these observations suggest that MGMT promoter methylation status may be partly a prognostic marker associated with the nature of the tumor, rather than a truly therapy- specific predictive marker. Cytochrome c Oxidase (CcO) is a mitochondrial enzyme involved in cellular ATP generation. We previously demonstrated that CcO plays a central role in acquired resistance to TMZ. Importantly, in a retrospective trial, we showed that CcO activity was inversely correlated with clinical outcomes. The long term goal is to identify robust and clinically relevant molecular markers that can add value to classical clinicl prognostic factors in order to tailor medical treatment to individual tumor characteristics and to design better clinical trials for new drugs against gliomas. The objective of the proposed biomarker clinical trial is to determine whether CcO activity represents a novel and valuable prognostic biomarker for patients receiving standard of care therapy. Our hypothesis is that high tumor CcO activity is associated with poor outcomes independently of MGMT promoter methylation status. Additionally, we hypothesize that MGMT promoter methylation status is a true predictive biomarker of how patients will respond to standard of care TMZ-based chemoradiation in tumors with low CcO activity. This will be tested by pursuing two specific aims: 1) determine overall and progression-free survival times relative to CcO activity; 2) compare the prognostic value of CcO activity to other commonly used prognostic markers. The approaches are innovative because we will validate activity of a mitochondrial enzyme, CcO, as a strong prognostic biomarker for primary GBM. Moreover, clinical trial designs based on CcO activity and MGMT promoter methylation stratification have tremendous potential to optimize and individualize therapy by prospectively identifying those patients who will benefit most from TMZ standard therapy and those who will not. This proposed research is significant because it is expected to vertically advance and expand the application of new prognostic and predictive biomarkers for GBM patients in order to tailor medical treatment based on individual tumor characteristics and to design better clinical trials for new drugs leading to personalized therapy for GBM patients.